Method And Apparatus For Pipe-Conveyed Well Logging

ABSTRACT

A well logging instrument deployment device according to this aspect of the invention includes a housing configured to be coupled to a pipe string. A latch disposed in the housing and is configured to retain a well logging instrument in a first longitudinal position inside the pipe string. An actuator is configured to release the latch to enable longitudinal movement of the well logging instrument inside the pipe string. A signal detector is operatively coupled to the actuator and is the configured to detect a command signal for operating the actuator.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of and claims priority toU.S. patent application Ser. No. 12/543,606, entitled “Method AndApparatus For Pipe-Conveyed Well Logging ” filed Aug. 19, 2009, theentire disclosure of which is hereby incorporated herein by reference.

FIELD OF THE DISCLOSURE

The invention relates generally to the field of well logging conveyance.More specifically, the invention relates to methods and devices forconveying well logging instruments through a wellbore.

BACKGROUND

Electric wireline wellbore logging instruments are used for, among otherthings, making measurements of various physical properties of earthformations penetrated by wellbores. Electric wireline logginginstruments are typically inserted into the wellbore by the force ofgravity while connected to the end of an armored electrical cable, andare returned to the earth's surface by retracting the cable. Forexample, the cable is typically retracted by a winch or similar spoolingapparatus. The cable provides electrical power to the instruments tooperate the various sensors and related devices therein and providessignal communication path(s) between the various sensors and relateddevices and a recording unit disposed at the Earth's surface.

Certain wellbores are drilled so as to have significant inclination fromvertical over at least a portion of the wellbore. Other wellbores canhave a section which is substantially horizontal. Still other wellboresmay be drilled through formations that are subject to swelling orcaving, or having fluid pressures therein that make passage of welllogging instruments past them that are unsuitable for typical welllogging instrument conveyance techniques. Gravity cannot be practicablyused to insert well logging instruments into these wellbores, so variousmethods have been devised to insert well logging instruments into suchwellbores.

One of the methods known in the art for inserting well logginginstruments into highly inclined or horizontal wellbores is to attachthe well logging instruments to the end of a pipe comprising threadedsections (“drill pipe” or “tubing”), and to lower the pipe into thewellbore by threadedly attaching additional sections to the pipe at theupper end thereof. After the well logging instruments are inserted to adesired depth in the wellbore, an electrical cable may be attached tothe upper end of the well logging instruments, typically by pumping thecable through the center of the pipe until the cable latches onto aspecial electrical and mechanical connector disposed at the top of thewell logging instruments. The cable can be inserted into the center ofthe pipe from the outside of the pipe through a device called a “sideentry sub.” A side entry sub is a short section of pipe having asealable opening through a side wall of the section of pipe, whichenables passage of the cable through the wall of the pipe section. Theside entry sub is typically assembled to the pipe at a substantialdistance below the upper end of the pipe. Assembled in this position,the side entry sub enables raising the well logging instruments withinthe wellbore (or withdrawing them from the wellbore) by removingsections from the pipe simultaneously with spooling of the cable as thelogging instruments are raised in or withdrawn from the wellbore. Bysuch procedure, portions of the wellbore can be measured with the welllogging instrument without repeated insertion and removal of the cablefrom the inside of the pipe.

A drawback to using pipe to convey the well logging instruments usingprocedures known in the art is the presence of the cable outside thepipe from the position of the side entry sub up to the earth's surface.In some cases control of fluids which may be present in the wellborerequires using equipment located at the earth's surface designed to sealan annular space between the pipe and the wellbore. In other cases it isnecessary to maintain fluid pressure on the wellbore from the earth'ssurface in order to obtain valid measurements from the instrumentsdisposed in the wellbore. Cable disposed outside the pipe disturbs theoperation of the sealing equipment and makes it difficult to seal thewellbore for maintaining fluid pressure.

Well logging instruments are also known in the art to be inserted intothe wellbore by using a coiled tubing having a coaxially insertedelectrical cable. Because the cable is coaxially inserted through thecoiled tubing, it is possible to seal the annular space between thewellbore and the coiled tubing with equipment similar to that used toseal the annular space outside the sectioned pipe.

U.S. Pat. No. 5,433,276 issued to Martain et al. described a method andapparatus for inserting electric wireline logging instruments into awellbore using an apparatus comprising pipe assembled from sections andcoiled tubing having a coaxially inserted armored electrical cable(“wireline”). The method includes the steps of attaching a first part ofa submersible electrical connector to one end of the coiled tubing andto the wireline inside the coiled tubing. A second part of thesubmersible connector is attached to one end of the wireline tools. Afirst part of a selectively operable latching mechanism is attached tothe same end of the wireline logging instruments. A second part of thelatching mechanism forms part of a latching sub which is attached to oneend of the pipe. The well logging instruments are attached to the pipeby engaging the first and second parts of the latching mechanism, andthe instruments are inserted into the wellbore to a predetermined depthby assembling the sections of the pipe. The coiled tubing is theninserted into the interior of the pipe until the submersible connectoris engaged. The latching mechanism is selectively operated to releasethe well logging instruments from the sub, and the coiled tubing isinserted further into the wellbore until the well logging instrumentsreach a desired depth. The coiled tubing is then withdrawn until theinstruments engage the sub. The latching mechanism is then selectivelyoperated so that the well logging instruments are attached to the sub.The coiled tubing is then withdrawn from the pipe, which disengages thesubmersible connector. The well logging instruments are then withdrawnfrom the wellbore by disassembling the sections of the pipe.

U.S. Pat. No. 4,041,780 issued to Angehrn describes a self-contained,battery powered well logging instrument that can be pumped down theinterior of a drill pipe string having a catcher sub at its lower end.When the well logging instrument latches into the catcher sub, thepumped fluid circulation is blocked, after which increased pump pressureswitches a valve assembly to recreate circulation and energize the welllogging instrument to a “standby” position. An accelerometer in the welllogging instrument detects the upward movement of the well logginginstrument and switches the circuitry from standby to a “record” mode.The output from a clock controlled by the downhole accelerometer isrecorded along with the logging information (measurements of formationproperties) measured by sensors on the well logging instrument and issynchronized with pipe footage measurements and with a similar suchaccelerometer and clock at the Earth's surface which are responsive tothe movement of the pipe string at the Earth's surface. The recordedlogging measurements are thus related to wellbore depth by correlatingwith the data simultaneously recorded at the Earth's surface. As analternative embodiment, the well logging instrument is attached to thedrill pipe prior to running the pipe into the wellbore.

U.S. Pat. No. 4,597,440 issued to Pottier and assigned to the assigneeof the present invention describes a method for displacing a welllogging instrument through a non-gravity descent portion of a wellboresuch as a highly deviated portion. The disclosed method includesassembling a well logging instrument at the lower end of a drill pipe asan exposed extension to the drill pipe, displacing the well logginginstrument thus exposed through the portion of the wellbore byconnecting additional sections of drill pipe and lowering the drillpipe, and, during this displacing, continuously generating and sendinguphole a signal indicative of the compressive load undergone by the welllogging instrument.

U.S. Pat. No. 4,457,370 issued to Wittrisch describes a method forperforming well logging or well servicing operations in a predeterminedinclined or horizontal zone of a well following an initial verticalportion thereof. The method includes fastening a logging instrument orwell servicing tool body at the end of a string of rods (such as drillpipe) lowered into the wellbore. The tool body includes an electricalconnector. The method includes lowering, at the end of an electricalcable, from the Earth's surface, a mating connector adapted to fit theconnector on the wellbore tool. Coupling the connectors is performed bythe action of a force generated at least partly by the pressure of afluid pumped through the pipe string, and supplying electric powerthrough the cable and the joined connectors to the well logging orservicing tool for its operation in the predetermined zone.

U.S. Pat. No. 6,578,631 issued to Milne et al. describes a method ofwell logging in which the well logging instrument is delivered to thebottom of the well within a drill pipe and then the well is logged bywithdrawing the drill pipe with the sensor portion of the well logginginstrument protruding from the drill pipe. Following the loggingoperation, the well logging instrument is returned to the surface byreverse circulation.

U.S. Pat. No. 6,755,257 issued to Spencer et al. describes an apparatusand method for deploying a compact battery/memory well logginginstrument for acquiring data in deviated or horizontal wellbores. Adrill pipe assembly includes a drill pipe having secured at a downholeend thereof a delatching latching sub. The delatching sub contains anextendable running sub supporting a battery/memory logging instrument.The running sub occupies an initial retracted position during deploymentof the drill pipe, whereby well the logging instrument is protectedwithin one or more drill pipe stands. The running sub is movable by amessenger to a second, extended position in which its logging instrumentprotrudes from the end of the drill pipe. The drill pipe assembly maytherefore be used to protect the well logging instrument during runningin operations; and then the logging instrument is extended out the endof the drill pipe for commencement of logging operations.

U.S. Pat. No. 6,269,891 issued to Runia discloses a system for drillingand logging of a wellbore drilled through subsurface formations. Thesystem includes a well logging instrument string and a drill stringhaving a longitudinal channel for circulation of drilling fluid. Thedrill string includes a port providing fluid communication between thechannel and the exterior of the drill string. The channel and the portare arranged to allow the well logging instrument string to pass throughthe channel and from the channel through the port to a position exteriorto the drill string. The system further includes a removable closureelement adapted to selectively close the port, wherein the logginginstrument string may be selectively connected to the closure element.

U.S. Patent Application Publication No. 2004/0118611 filed by Runiadiscloses a method of drilling a wellbore into subsurface formationsis-provided, including using a drill string which includes at its lowerend a bottom hole assembly comprising a drill bit, a drill steeringsystem, and a surveying system, wherein the drill string includes apassageway for an auxiliary tool to move from a first position interiorof the drill string above the bottom hole assembly to a second position,wherein at least part of the auxiliary tool is exterior to the drillstring below the bottom hole assembly. The passageway can be selectivelyclosed. The method also includes drilling so as to progress the drillstring into the formations until a tool operating condition is met;opening the passageway; passing an auxiliary tool from the firstposition through the passageway to the second position, and operatingthe auxiliary tool at the second position.

U.S. Pat. No. 7,134,493 issued to Runia discloses a well logging systemthat may be used in a wellbore. A tubular conduit extends from theEarth's surface into the wellbore and contains a body of wellbore fluid.A well logging instrument string may be passed from a position withinthe conduit to a position outside the conduit at a lower end partthereof, and may be suspended by the conduit in the position outside theconduit. A pressure pulse device is arranged within the conduit in amanner that the pressure pulse device is in data communication with thewell logging instrument string. The pressure pulse device is capable ofgenerating pressure pulses in the body of wellbore fluid, which pressurepulses represent data communicated by the well logging instrument stringto the pressure pulse device during logging of earth formation by thewell logging instrument string. The system further includes a controlsystem in fluid communication with the body of wellbore fluid andarranged to receive the pressure pulses.

U.S. Patent Application Publication No. 2004/0238218 filed by Runia etal.

discloses a method and system for introducing a fluid into a borehole,in which there is arranged a tubular drill string including a drill bit.The drill bit is provided with a passageway between the interior of thedrill string and the borehole, and with a removable closure element forselectively closing the passageway in a closing position. There isfurther provided a fluid injection tool comprising a tool inlet and atool outlet. A method disclosed in the '218 publication includes passingthe fluid injection tool through the drill string to the closureelement, and using it to remove the closure element from the closingposition; passing the fluid injection tool outlet through thepassageway, and introducing the fluid into the borehole from theinterior of the drill string through fluid injection tool into theborehole.

There continues to be a need for well logging instrument conveyancemethods and apparatus that reduce the risk of damage to the well logginginstruments and increase the reliability of moving the logginginstruments into and out of wellbores where wellbore conditions makeinstrument conveyance difficult and risky.

SUMMARY

One aspect of the invention is a well logging instrument deploymentdevice. A well logging instrument deployment device according to thisaspect of the invention includes a housing configured to be coupled to apipe string. An actuator is configured to release the well logginginstrument from within the pipe string to enable longitudinal movementof the well logging instrument inside the pipe string. A device forterminating longitudinal motion of the well logging instrument at asecond longitudinal position when a selected portion of the logginginstrument is exposed below an end of the pipe string. The device forterminating longitudinal motion includes a tapered retaining keyconfigured to cooperatively engage a groove in an exterior of the welllogging instrument.

A method for well logging according to another aspect of the inventionincludes releasing a well logging instrument from a conveyance device.The method also includes moving the well logging instrumentlongitudinally inside a pipe string until a device for terminatinglongitudinal motion of the well logging instrument engages a groove inan exterior of the well logging instrument with a tapered retaining key.

Other aspects and advantages of the invention will be apparent from thefollowing description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a well logging instrument disposed in one example of adeployment device coupled to a drill string disposed in a wellbore.

FIG. 1A shows the logging instrument latched in place inside the pipestring prior to deployment.

FIG. 1B shows the logging instrument deployed partially outside the pipestring.

FIGS. 2 through 6 show various examples of latch release actuators.

FIG. 7 shows another example of logging instrument deployed outside thepipe string.

DETAILED DESCRIPTION OF THE INVENTION

An example well logging instrument deployment device includes aconveyance device that can be coupled to a pipe string. The logginginstrument deployment device includes an actuator configured to releasethe well logging instrument from within the pipe string so that thelogging instrument extends at least partially out from an end of thepipe string. The actuator can be a fusible link trigger, such asdescribed in U.S. Pat. No. 6,431,269 entitled “Electrically ControlledRelease Device”, which is incorporated herein in its entirety. Theactuator can be any other now known or future known actuator, includinga paw and latch system, or the like. The example well logging instrumentdeployment device can include a device for terminating longitudinalmotion of the well logging instrument at a second longitudinal positionwhen a selected portion of the logging instrument is exposed below anend of the pipe string. The device for terminating longitudinal motionincludes a tapered retaining key configured to cooperatively engage agroove in an exterior of the well logging instrument.

An example well logging system according to various aspects of theinvention in which one or more well logging instruments is conveyedthrough a wellbore is shown schematically in FIG. 1. A drilling rig 24or similar hoisting device suspends a pipe string 20 in a wellbore 18drilled through subsurface rock formations 11. The pipe string 20 isgenerally assembled by threadedly coupling together end to end aplurality of individual segments (“joints”) 22 of drill pipe or otherthreadedly connected pipe. To extend the axial length (depth) of thewellbore 18, hoisting equipment (not shown separately) on the rig 24releases the pipe string 20 to cause some of its weight to be applied toa drill bit 14, which may be disposed at the bottom end of the pipestring 20. A top drive 26 or a functionally equivalent device (e.g.,kelly, kelly bushing and rotary table) on the rig 24 may be used torotate the pipe string 20, or an hydraulic motor (not shown in FIG. 1)disposed in the pipe string 20 may perform such rotation of thecomponents below it in the pipe string 20. A pump 32 lifts drillingfluid 30 (“mud”) from a storage tank or pit 28 and discharges the mud 30under pressure through a standpipe and hose combination 34 into the topdrive 26. The mud 30 travels under pressure through various rotary seals(not shown) in the top drive and then into the interior of the pipestring 20. The mud eventually is discharged through nozzles or courses(not shown) in the bit 14 so that the mud 30 cools and lubricates thebit 14, provides hydrostatic pressure to prevent entry of fluids fromthe formations 11 into the wellbore 18 and lifts drill cuttings to thesurface for disposal.

In the example of FIG. 1, a well logging instrument or an assembly of aplurality of such instruments (referred to for convenience collectivelyhereinafter as “logging instruments”) is shown generally at 10 disposedinside the pipe string 20 at a selected position typically above thedrill bit 14, and generally disposed longitudinally completely insidethe pipe string 20. In other examples, the pipe string 20 may excludethe drill bit 14 and have an open lower end. The logging instruments 10may be retained in the selected position inside the pipe string 20 by acontrollable latch 12 which will be described in more detail below. Theterm logging instruments is included to mean, without limitation anydevice for measuring a property of the formations 11, ambient conditionsin the wellbore 18 (e.g., pressure, temperature, fluid density) and/ormechanical properties of the wellbore 18 and the interior of the pipestring (e.g., a caliper). The term logging instruments may also meandevices that are used to withdraw samples of the formations 11 orsamples of fluid contained in the pore spaces thereof.

A purpose of the system shown in FIG. 1 is to enable use of the pipestring 20 to convey the logging instruments 10 beyond places (not shownseparately) in the wellbore 18 where conveyance by other techniques,including by gravity at the end of a cable, by coiled tubing, or bybeing fixedly coupled at the end of the pipe string 20 may beundesirable, unsafe or impracticable. Those skilled in the art will befamiliar with the conditions under which conveyance of logginginstruments disposed inside drill pipe is desirable and effective and sothese will not be described in detail herein. When using the systemshown in FIG. 1, the logging instruments are latched in place within thepipe string 20 generally as shown, and the pipe string 20 is loweredinto the wellbore 18. Once the pipe string 20 has been moved so that thelogging instruments 10 are considered to be safely beyond any suchadverse wellbore condition, it may then be desired to operate thelogging instruments 10 to make measurements of properties of theformations 11 outside the wellbore 18 or to perform other operations asis consistent with the broadly applied term “logging instruments.” Toperform such operations, the latch 12 is released to enable the logginginstruments 10 to extend through the bottom end of the pipe string 20,or through an opening in the drill bit 14, if particular types of drillbits are used on the pipe string 20 that enable such movement. See, forexample, U.S. Pat. No. 6,269,891 issued to Runia or U.S. Pat. No.5,244,050 issued to Estes for non-limiting examples of such drill bits.

Upon being extended through the end of the pipe string 20 by a selectedlength, the logging instruments 10 may be latched in such place in thepipe string 20 or otherwise restrained from further movement out of thebottom of the pipe string 20. The logging instruments may be operated inplace, and/or the pipe string 20 may then be withdrawn from the wellbore18 while sensors (e.g., see FIG. 1B) in the logging instruments 10 makemeasurements of selected parameters of the formations 11 outside thewellbore 18 and/or of the physical characteristics of the wellbore 18,such as its diameter. Details of examples by which the latch 12 isoperated to enable extension of the logging instruments 10 beyond theend of the pipe string 20 is initiated will be further explained belowwith reference to FIGS. 1A and 1B.

In some examples, the latch 12 may be caused to operate to release thelogging instruments 10 by application of suitable fluid pressure to theinterior of the pipe string 20. Such pressure may be, for example, aselected absolute pressure value, or may be a coded sequence ofincreases and decreases in pressure. Such pressure may be applied bysuitable operation of the pump 32, or by a supplemental pump (not shown)and/or by a bypass valve (not shown) in pressure communication with thepump 32. Examples of the latter two devices as may be used in someimplementations are described in U.S. Pat. No. 4,856,595 issued toUpchurch and assigned to the assignee of the present invention. Thefluid pressure to operate the latch may be measured by a sensor 36 thatis in signal communication with a recording unit 42. The sensor 36 maybe a pressure sensor, a flow sensor, a plurality of sensors, such asdifferential pressure sensors, or other types of sensors that may beused to measure changes in the fluid properties. For example, the sensor36 may measure changes in the flow rate, such as a sequence in the flowrate, and decipher or otherwise determine a command signal based onthese changes to the flow rate. The recording unit 42 can includeequipment (not shown separately) for making a record with respect totime of measurements made by various sensors in the logging instruments10, the depth of the pipe string 20 in the wellbore 18 and the pressure,among other parameters. Communication of signals from the sensor 36 tothe recording unit 42 is shown as wireless, however such communicationis not a limit on the scope of the invention.

In some examples, the pipe string 20 may be a so called “wired” pipestring and include therewith a signal communication channel such as awire or cable (not shown) associated with each pipe joint 22 and acommunication coupling (not shown) at the longitudinal ends of each pipejoint 22 to enable signal communication along the wired pipe string 20.Non-limiting examples of such wired pipe strings and associatedcommunication devices are described in U.S. Patent ApplicationPublication No. 2006/0225926 filed by Madhavan et al., the underlyingpatent application for which is assigned to the assignee of the presentinvention and U.S. Pat. No. 6,641,434 issued to Boyle et al. alsoassigned to the assignee of the present invention. When such “wired”pipe strings are used, the logging instruments 10 may include signalcommunication devices (explained below) to maintain signal communicationusing the communication channel (not shown) in the wired pipe string 20.Signal communication may also be maintained between the recording unit42 and the channel (not shown) in the wired pipe string 20 by atransceiver 40 associated with the recording unit and a transceiver 38associated with the top drive 26. Such transceivers 38, 40 enable freemovement of the pipe string 20 while maintaining the above describedsignal communication.

FIG. 1A shows a more detailed cross section of the logging instruments10 locked in place inside the pipe string 20 by the latch 12 prior todeployment. The entire assembly of components may be disposed inside ahousing 20A that may be configured from one or more joints of pipe(e.g., 22 in FIG. 1), which as will be further explained may in someexamples be wired drill pipe. The logging instruments 10 may begenerally enclosed in a pressure resistant housing 10A such as may bemade from stainless steel, titanium or other high strength, corrosionresistant material. The housing 10A may include a retaining groove 50 orsimilar feature on its exterior surface into which a first retaining key52 extends from the latch 12. The latch 12 may be fixedly disposedinside the pipe string 20 so that extension of the first retaining key52 into the groove 50 will prevent longitudinal movement of the logginginstruments 10 in the pipe string 20.

In the present example, the latch 12 may be configured to be operated bya control signal from the surface (e.g., the recording unit 42). Oneexample control signal includes applying a particular pressure or codedsequence of pressure to the interior of the pipe string 20 as explainedabove with reference to FIG. 1. A pressure sensor 15 may be disposedproximate the latch 12 or can be associated therewith and can detect thefluid pressure inside the pipe string 20. Output of the pressure sensor15 may be conducted to a controller 17 such as a microprocessorassociated with the latch 12. The controller 17, upon determining fromthe measured pressure that a release command has been transmitted fromthe surface, will cause operation of an actuator 19. Operation of theactuator 19, several examples of which will be explained below withreference to FIGS. 2 through 6, causes the first retaining key 52 tomove out of the retaining groove 50, or enables it to bend outwardly if,for example, the retaining key 52 is disposed on a spring metalstructure. Movement of the retaining key 52 out of the groove enablesthe logging instruments 10 to move longitudinally downwardly through theinterior of the pipe string 20. Longitudinal movement may be by gravityor may be performed by operating the pump (32 in FIG. 1) to move mud (30in FIG. 1) through the interior of the pipe string 20.

Another example of operating the actuator 19, applicable to the casewhere the pipe string 20 is a wired pipe string as explained above, isto include a communication coupling 78 in the pipe string 20 proximate aselected position on the latch 12, and to provide a correspondingcommunication coupling 79 proximate thereto and associated with thelatch 12. The communication coupling 78 in the pipe string 20 may be insignal communication with the communication channel (not shown) in thewired pipe string 20. Commands to operate the latch 12 may betransmitted over the wired pipe string, through the communicationcouplings 78, 79 and to the controller 17 to operate the actuator 19 ina manner similar to the pressure-controlled actuation described above.

In the present example, a second retaining key 72 may be disposed in asuitable position inside the pipe string 20 longitudinally displacedfrom the latch 12 so that movement of the logging instruments 10 islimited. Typically, such limit will provide that sensor-containingportions (not shown in FIG. 1A) of the logging instruments 10 extendinto the wellbore (18 in FIG. 1) below the bottom of the pipe string 20.A possible alternative to using the second retaining key 72, can be toprovide a diameter of an opening in the lower end of the pipe string 20(or drill bit 14 in FIG. 1) and a corresponding outer diameter ofportion of the logging instrument housing 10A selected such that only aportion of the housing 10A may pass therethrough, causing the remainingportion of the housing 10A to be retained inside the pipe string 20.

In examples wherein the pipe string 20 is a wired pipe string asexplained with reference to FIG. 1, the second retaining key 72 may beassociated with a data communication link 70. The data communicationlink 70 may include a communication coupling 74 positioned in the datacommunication link 70 so that when the logging instruments 10 arelatched in place by the second retaining key 72, a communication link 13disposed in a suitable position inside the logging instrument housing10A will be positioned longitudinally proximate the communicationcoupling 74 so that the logging instrument's communication link 13 cantransfer signals between the logging instruments 10 and thecommunication coupling 74. The communication link 70 can be configuredto communicate signals between the communication link 70 and acommunication device 76 disposed in the wired pipe string 20 similar tothose described above (i.e., 78, 79) with respect to the latch 12.Non-limiting examples of electromagnetic communication devices fortransferring signals between logging instruments and ancillary devicessuch as the communication link 70 are shown in U.S. Pat. No. 5,521,592issued to Veneruso and assigned to the assignee of the presentinvention.

The second retaining key 72 may be configured, for example, by suitabletapering, to enable free movement of the logging instruments 10 in anupward direction, back inside the pipe string 20, while preventingfurther downward movement. As may be necessary during operations, thelogging instruments 10 may be withdrawn longitudinally fully back insidethe pipe string 20, for example, by reverse pumping of the mud (30 inFIG. 1) or by attaching a suitable retrieval device (not shown in FIG.1A) to a “fishing neck” 10B or similar retrieval feature on the top ofthe logging instrument housing 10A. The logging instruments 10 may alsobe fully withdrawn from the pipe string 20 in such configurations. Onenon-limiting example of a technique for withdrawing the logginginstruments is to insert a winch deployed “slickline” (not shown) with asuitable latch (not shown) to couple to the fishing neck 10B to retrievethe logging instruments 10.

FIG. 1B shows the logging instruments 10 in a deployed positionextending at least partially outwardly below the bottom of the pipestring 20. As explained with reference to FIG. 1, some pipe strings mayinclude a drill bit (e.g., 14 in FIG. 1) at the lower end thereofconfigured to enable movement of the logging instruments 10therethrough, although the example in FIG. 1B does not show such a drillbit. After release of the first retaining key (19 in FIG. 1A) in thelatch (12 in FIG. 1A), the logging instruments 10 may move downwardlythrough the pipe string 20 for example, by gravity or by pumping mud (30in FIG. 1) until the second retaining key 72 seats in the groove 50,thus preventing further downward movement of the logging instruments 10.In wired pipe string configurations, such as shown in FIG. 1B, signalcommunication to the recording unit (42 in FIG. 1) may be performedusing the electromagnetic coupling components 13, 74, 76 described aboveto transfer signals to and from the communication channel (not shownseparately) in the wired pipe string 20. In pipe strings not using orhaving a communication channel, signals detected by various sensors inthe logging instruments 10 may be recorded in a data storage device (notshown separately) in the logging instruments 10.

Examples of logging instruments that may be used include, withoutlimitation, electromagnetic induction or galvanic resistivitymeasurement devices 78, natural gamma spectroscopy devices 80,gamma-gamma density/photoelectric effect measurement devices 82 andneutron hydrogen index measurement devices 84. Other well logginginstruments will occur to those skilled in the art that may be used inaccordance with the present invention and the examples shown in FIG. 1Bare not intended to limit the scope of the invention.

FIGS. 2 through 6 show various examples of devices to release the firstretaining key (52 in FIG. 1A). The general principle of all the releasemechanisms in FIGS. 2 through 6, and generally with reference to FIG. 2,is the use of a release pawl 54, that prior to release of the logginginstruments 10 is disposed over the end of the first release key 52 sothat it remains depressed in the groove 50, thus locking the logginginstruments 10 in position inside the pipe string 20. When the releasepawl 54 is moved longitudinally as indicated by the arrow in FIG. 2 sothat it no longer covers the first retaining key 52, the first retainingkey 52 is free to move laterally outwardly from the groove 50.

Referring to FIG. 3, one way to enable the first retaining key 52 toself-release from the groove is to mount it to the latch 12 using aspring steel connector bar 53. The same connector bar 53 may be used inall the examples to be explained with reference to FIGS. 3 through 6.The example shown in FIG. 3 includes an hydraulic cylinder 56 with apiston 58 disposed therein. Suitable components (not shown) in the latch(12 in FIG. 2) may cause the piston 58 to retract the release pawl 54upon receipt of a release command as explained above.

An example shown in FIG. 4 includes a motor 62 and worm gear 60operatively coupled to the release pawl 54. The motor 62 can be operatedupon receipt of the release command in the latch (12 in FIG. 2) torotate the screw 60 and thus retract the release pawl. 54.

Another example is shown in FIG. 5, in which the release pawl 54 iscoupled to a spring 64. The spring 64 is held in place by a retainer 66which may be an electrically operated solenoid or piston/cylinder (e.g.,as shown in FIG. 3). Operation of the retainer 66 causes the spring topull the release pawl 54 to enable release of the first retaining key52.

FIG. 6 shows a spring operated version of the release pawl 54 actuatorin which the spring 64 is released by using, for example, an explosivesquib 68. Other devices for actuating the release pawl will occur tothose of ordinary skill in the art.

In another example shown in FIG. 7, the well logging instruments 10 maybe flexibly deployed through the end of the pipe string 20 (with orwithout a special drill bit 14 as described above) in order that certainsensors are enabled to contact the wall of the wellbore 18. The housing10A is shown retained in place by the second retaining key 72 as in theexample shown in FIG. 1B. In the present example, signal communicationmay be wired as shown and/or sensor signals may be stored in the logginginstruments 10 as explained above. The housing 10A may be coupled at itslower end to one end of a segment 92 of armored electrical cable of anytype ordinarily used to covey wireline instruments in a wellbore. Thesegment 92 may be coupled at its other end to a tool head 90 of any typewell known in the art for coupling electrical cable to well logginginstruments. The remainder of the sensors and other devices in thelogging instruments (84 and 82 shown in FIG. 7) may be coupled below thetool head 90. As can be observed in FIG. 7, the cable segment 92 enablesthe logging instruments 10 to be substantially laterally displaced fromthe housing 10A and the center line of the pipe string 20. The logginginstruments 10 may be operated substantially as explained with referenceto FIG. 1C. Should it be desirable or necessary to return the logginginstruments 10 fully to the interior of the pipe string 20, a suitabledevice may be coupled to the fishing neck 10B as in the previousexample, and the logging instruments 10 withdrawn back inside the pipestring 20. While a cable segment 92 is shown coupling the housing 10A tothe various devices below, it will be readily appreciated that otherflexible members known in the art can perform the equivalent function ofenabling the logging instruments 10 to laterally deflect from the pipestring 20. Non-limiting examples include flex joints, knuckles,universal joints and similar devices. The example shown in FIG. 7, aswell as the foregoing additional examples, may have advantages for usewith sensors that operate better when in contact with the wellbore wall,for example, density and neutron hydrogen index sensors.

A well logging tool conveyance system according to the various aspectsof the invention may be provide more reliable, safer release of the welllogging instruments into open wellbore below a pipe string than devicesknown in the art prior to the present invention.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A well logging instrument deployment device,comprising: a conveyance device configured to be coupled to a pipestring; an actuator configured to release the well logging instrumentfrom within the pipe string so that the logging instrument extends atleast partially out from an end of the pipe string; and a device forterminating longitudinal motion of the well logging instrument at asecond longitudinal position when a selected portion of the logginginstrument is exposed below an end of the pipe string, wherein thedevice for terminating longitudinal motion comprises a tapered retainingkey configured to cooperatively engage a groove in an exterior of thewell logging instrument.
 2. The device of claim 1, wherein the actuatorcomprises a device for moving a release pawl away from a retaining key,the retaining key disposed in a corresponding retaining groove in anexterior of the well logging instrument.
 3. The device of claim 2,wherein the device for moving the release pawl comprises at least one ofan explosive squib, a motor and gear assembly, an electrically operatedsolenoid and an hydraulic cylinder and piston.
 4. The device of claim 1,wherein the actuator is a fusible link trigger.
 5. A method for welllogging, comprising: releasing a well logging instrument from aconveyance device; and moving the well logging instrument longitudinallyinside the pipe string until a device for terminating longitudinalmotion of the well logging instrument engages a groove in an exterior ofthe well logging instrument with a tapered retaining key.
 6. The methodof claim 5, wherein releasing a well logging instrument from aconveyance device comprises actuating an electric release device.
 7. Thedevice of claim 5, wherein releasing a well logging instrument from aconveyance device comprises moving a release pawl away from a retainingkey.
 8. A well logging system comprising: a pipe string; and aninstrument deployment device comprising: a conveyance device configuredto be coupled to the pipe string; an actuator configured to release awell logging instrument from a first longitudinal position within thepipe string; and a device for terminating longitudinal motion of thewell logging instrument at a second longitudinal position when aselected portion of the logging instrument is exposed below an end ofthe pipe string, wherein the device for terminating longitudinal motioncomprises a tapered retaining key configured to cooperatively engage agroove in an exterior of the well logging instrument.
 9. The device ofclaim 8, wherein the actuator comprises a device for moving a releasepawl away from a retaining key, the retaining key disposed in acorresponding retaining groove in an exterior of the well logginginstrument.
 10. The device of claim 9, wherein the device for moving therelease pawl comprises at least one of an explosive squib, a motor andgear assembly, an electrically operated solenoid and an hydrauliccylinder and piston.
 11. The device of claim 8, wherein the actuator isfusible link trigger.